JP7580358B2 - Optical fiber connection structure and optical fiber connection method - Google Patents

Description

The present invention relates to an optical fiber connection structure and an optical fiber connection method.

Technology has been proposed for installing optical fibers in structures to detect strain occurring in the structures. For example, Patent Document 1 discloses a technology for embedding optical fibers housed in a covering pipe material in prefabricated piles. The optical fibers embedded in the prefabricated piles are connected to each other by various couplers.

JP 2003-213676 A

However, in the above-mentioned technology, the connection between the optical fibers is weaker than the optical fiber core itself, so if an external force is applied to the connection between the optical fibers, there is a risk of the optical fiber breaking.

The present invention aims to provide an optical fiber connection structure and an optical fiber connection method that can reduce the possibility of optical fiber breakage.

The present invention is an optical fiber connection structure comprising a first optical fiber, a first tube member housing the first optical fiber, a second optical fiber, a second tube member housing the second optical fiber, a connection portion between the first optical fiber and the second optical fiber, and a third tube member, the first tube member and the third tube member being integrated, the second tube member and the third tube member being integrated, and the connection portion being housed in any of the first tube member, the second tube member, and the third tube member, and being movable relative to the first tube member, the second tube member, and the third tube member.

According to this configuration, the optical fiber connection structure includes a first optical fiber, a first tube member that houses the first optical fiber, a second optical fiber, a second tube member that houses the second optical fiber, a connection portion between the first optical fiber and the second optical fiber, and a third tube member, the first tube member and the third tube member are integrated, the second tube member and the third tube member are integrated, and the connection portion is housed in any of the first tube member, the second tube member, and the third tube member and is movable relative to the first tube member, the second tube member, and the third tube member. Therefore, even if a force is applied from the outside to the first tube member, the second tube member, or the third tube member, distortion is unlikely to occur in the connection portion, and the possibility of the optical fiber being broken can be reduced.

In this case, the first optical fiber may be fixed to the first tube member so as not to be movable, and the second optical fiber may be fixed to the second tube member so as not to be movable.

With this configuration, the first optical fiber is fixed to the first tube member so that it cannot move freely, and the second optical fiber is fixed to the second tube member so that it cannot move freely. Therefore, by integrating the first tube member and the second tube member with the structure, it is possible to measure the strain generated in the structure.

In addition, the third tube member may be bent, and the first tube member and the second tube member integrated with the third tube member may extend in different directions.

With this configuration, the third tube member is bent, and the first and second tube members integrated with the third tube member extend in different directions. For example, when installing an optical fiber at the intersection of two reinforcing bars, the first tube member is attached to one reinforcing bar, the second tube member is attached to the other reinforcing bar, and the third tube member is placed at the intersection. This reduces the possibility of the optical fiber breaking while improving the ease of installation.

The present invention is an optical fiber connection method that includes an optical fiber connection step of connecting a first optical fiber housed in a first tube member and a second optical fiber housed in a second tube member with a connection part, and a connection part accommodation step of integrating the first tube member and the third tube member and integrating the second tube member and the third tube member so that the connection part connected in the connection step is housed in one of the first tube member, the second tube member, and the third tube member and can move freely relative to the first tube member, the second tube member, and the third tube member.

In this case, in the optical fiber connection process, the first optical fiber may be fixed to the first tube member so as not to be movable, and the second optical fiber may be fixed to the second tube member so as not to be movable.

In addition, in the connection portion accommodation process, the third pipe member may be bent, and the first pipe member and the second pipe member integrated with the third pipe member may extend in different directions.

The optical fiber connection structure and optical fiber connection method of the present invention can reduce the possibility of optical fiber breakage.

1A is a diagram showing an optical fiber connecting step of an optical fiber connecting method according to an embodiment, and FIG. 1B is a cross-sectional view showing a first optical fiber and a first tube member of FIG. 4A to 4C are diagrams illustrating a connection portion accommodating step of the optical fiber connection method according to the embodiment, and an optical fiber connection structure. 11A to 11C are diagrams illustrating a connection portion accommodating step of the optical fiber connection method according to the embodiment and another example of an optical fiber connection structure.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The optical fiber connection method and optical fiber connection structure of this embodiment are applied, for example, when connecting optical fibers using fusion splicing or a connector. As shown in Figures 1(A) and 1(B), an optical fiber connection process is performed in which a first optical fiber 11 housed in a first tube member 21 and a second optical fiber 12 housed in a second tube member 22 are connected at a connection portion 30.

For example, the first pipe member 21 and the second pipe member 22 are pipes made of polyvinyl chloride or the like having unevenness (thread joints) on the outer surface for adhesion to concrete. In the optical fiber connection process, the first optical fiber 11 is fixed to the first pipe member 21 so as not to move freely, and the second optical fiber 12 is fixed to the second pipe member 22 so as not to move freely. Specifically, the first optical fiber 11 is bonded to the inner surface of the first pipe member 21, and the second optical fiber 12 is bonded to the inner surface of the second pipe member 22. An unbonded portion necessary for connection at the connection portion 30 between the first optical fiber 11 and the second optical fiber 12 is provided at the end of the first pipe member 21 and the end of the second pipe member 22. The number of first optical fibers 11 housed in the first pipe member 21 and the number of second optical fibers 12 housed in the second pipe member 22 may be any number.

Either the first pipe member 21 or the second pipe member 22 is surrounded by a third pipe member 23A, 23B whose inner diameter is slightly larger than the outer diameter of the first pipe member 21 and the second pipe member 22. The third pipe members 23A, 23B are pipes made of, for example, polyvinyl chloride. The inner surface of the third pipe member 23A is provided with irregularities (thread joints) that can be fitted into the thread joints of the first pipe member 21 and the second pipe member 22.

The third pipe member 23B, which corresponds to the intersection of the rebars where the wiring direction of the first optical fiber 11 and the second optical fiber 12 changes by 90°, is bent at 90°. The outer diameter of the third pipe member 23B is slightly smaller than the inner diameter of the third pipe member 23A. The inner surfaces of the third pipe members 23A and 23B are provided with irregularities (thread joints) that can fit with the thread joints of the first pipe member 21 and the second pipe member 22. In addition, the outer surface of the third pipe member 23B is provided with irregularities (thread joints) that can fit with the thread joints on the inner surface of the third pipe member 23A.

In the example of FIG. 1(A), a third tube member 23A is disposed in the first tube member 21 in the center of FIG. 1(A). A third tube member 23A is disposed in the second tube member 22 on the left side of FIG. 1(A). The second tube member 22 on the right side of FIG. 1(A), which corresponds to the intersection of the rebars where the wiring direction of the first optical fiber 11 and the second optical fiber 12 changes by 90°, extends at an angle of 90° to the first tube member 21. A third tube member 23B is disposed at the end of the second tube member 22 on the right side of FIG. 1(A) on the first tube member 21 side.

The first tube member 21 containing the first optical fiber 11 and the second tube member 22 containing the second optical fiber 12 are tied to a reinforcing bar (not shown) and installed at a predetermined position. The first tube member 21 and the second tube member 22 on the left side of FIG. 1(A) are temporarily fixed in a state in which the end of the first tube member 21 and the end of the second tube member 22 on the left side of FIG. 1(A) are spaced apart by a length necessary for connecting the first optical fiber 11 and the second optical fiber 12 at the connecting portion 30. The first tube member 21 and the second tube member 22 on the right side of FIG. 1(A) are temporarily fixed in a state in which the end of the first tube member 21 and the end of the third tube member 23B arranged in the second tube member 22 on the right side of FIG. 1(A) are spaced apart by a length necessary for connecting the first optical fiber 11 and the second optical fiber 12 at the connecting portion 30.

The first optical fiber 11 housed in the first tube member 21 and the second optical fiber 12 housed in the second tube member 22 are connected at the connection part 30. The first optical fiber 11 and the second optical fiber 12 are connected at the connection part 30 by, for example, fusion splicing.

As shown in FIG. 2, the connection part 30 connected in the connection process is accommodated in either the first pipe member 21, the second pipe member 22, or the third pipe member 23A, 23B, and a connection part accommodation process is performed to integrate the first pipe member 21 and the third pipe members 23A, 23B and integrate the second pipe member 22 and the third pipe members 23A, 23B so that the connection part 30 can move freely relative to the first pipe member 21, the second pipe member 22, and the third pipe members 23A, 23B.

In the connection portion accommodation step, the end of the first tube member 21, which is temporarily fixed in a separated state for the connection at the connection portion 30 between the first optical fiber 11 and the second optical fiber 12, is butted against the end of the second tube member 22 on the left side of FIG. 1(A). The connection portion 30 is accommodated inside either the first tube member 21 or the second tube member 22. Also, the end of the first tube member 21, which is temporarily fixed in a separated state for the connection at the connection portion 30 between the first optical fiber 11 and the second optical fiber 12, is butted against the end of the third tube member 23B arranged in the second tube member 22 on the right side of FIG. 1(A). The connection portion 30 is accommodated inside either the first tube member 21 or the third tube member 23B.

The third pipe member 23A arranged on the second pipe member 22 on the left side of FIG. 2 is rotated and moved so as to straddle the second pipe member 22 and the first pipe member 21 on the left side of FIG. 2 by the screw joints on the outer surfaces of the second pipe member 22 and the first pipe member 21, which fit together, and the screw joints on the inner surface of the third pipe member 23A. The third pipe member 23A arranged on the first pipe member 21 in the center of FIG. 2 is rotated and moved so as to straddle the first pipe member 21 in the center of FIG. 2 and the third pipe member 23B arranged on the second pipe member 22 on the right side of FIG. 2 by the screw joints on the outer surfaces of the first pipe member 21 and the third pipe member 23B, which fit together, and the screw joints on the inner surface of the third pipe member 23A.

As a result, the connection part 30 connected in the connection process is accommodated in one of the first pipe member 21, the second pipe member 22, and the third pipe member 23A, 23B, and the first pipe member 21 and the third pipe member 23A, 23B are integrated, and the second pipe member 22 and the third pipe member 23A, 23B are integrated so that the connection part 30 can move freely relative to the first pipe member 21, the second pipe member 22, and the third pipe member 23A, 23B. In the example of FIG. 2, in the connection part accommodation process, the third pipe member 23B is bent, and the first pipe member 21 and the second pipe member 22 integrated with the third pipe member 23B extend in different directions.

In this manner, the optical fiber connection structure 1 of this embodiment is formed. The optical fiber connection structure 1 of this embodiment includes a first optical fiber 11, a first tube member 21 that houses the first optical fiber 11, a second optical fiber 12, a second tube member 22 that houses the second optical fiber 12, a connection portion 30 between the first optical fiber 11 and the second optical fiber 12, and third tube members 23A and 23B, the first tube member 21 and the third tube members 23A and 23B are integrated, the second tube member 22 and the third tube members 23A and 23B are integrated, and the connection portion 30 is housed in one of the first tube member 21, the second tube member 22, and the third tube members 23A and 23B, and is movable relative to the first tube member 21, the second tube member 22, and the third tube members 23A and 23B.

In addition, in this embodiment, the first optical fiber 11 and the second optical fiber 12 are fixed to the first tube member 21 and the second tube member 22, which are integrated with the structure, so as to be immovable, respectively, in order to measure the strain occurring in the structure. Note that the first optical fiber 11 housed in the first tube member 21 does not necessarily have to be fixed to the first tube member 21 so as to be immovable, and the second optical fiber 12 housed in the second tube member 22 does not necessarily have to be fixed to the second tube member 22 so as to be immovable. In this case, the mechanical strain occurring in the structure is not transmitted to the first optical fiber 11 and the second optical fiber 12, so it becomes possible to measure only the temperature change.

The shapes of the first pipe member 21, the second pipe member 22, and the third pipe member 23A, 23B may be any shape other than a round pipe. The material of the first pipe member 21, the second pipe member 22, and the third pipe member 23A, 23B may be any material such as a synthetic resin other than polyvinyl chloride or a metal. The material of the first pipe member 21, the second pipe member 22, and the third pipe member 23A, 23B is preferably one that has a low elastic modulus, a high yield strength, and excellent corrosion resistance.

The first optical fiber 11 and the second optical fiber 12 are directly inserted into the first tube member 21 and the second tube member 22 and are integrated by filling them with adhesive (filler). In addition, the first tube member 21 and the second tube member 22 are divided in a longitudinal section along the longitudinal direction, and then the first optical fiber and the second optical fiber are integrated with adhesive on the inner surface of the first tube member 21 and the second tube member 22, and the divided first tube member 21 and the second tube member 22 are integrated again. Both ends of the first optical fiber 11 and the second optical fiber 12 protrude from both ends of the first tube member 21 and the second tube member 22.

In the optical fiber connection process, the connection at the connection portion 30 between the first optical fiber 11 and the second optical fiber 12 may be a connector connection using any connector, not fusion. In the connection portion accommodation process, the end of the first tube member 21 and the end of the second tube member 22 do not necessarily have to be butted together. In the connection portion accommodation process, the end of the first tube member 21 and the end of the third tube member 23B arranged in the second tube member 22 do not necessarily have to be butted together. In addition, the first tube member 21, the second tube member 22, and the third tube members 23A and 23B do not necessarily have to be fixed to reinforcing bars. The optical fiber connection structure and the optical fiber connection method of this embodiment are applicable regardless of the presence or absence of reinforcing bars.

The unevenness (screw knots) on the outer surfaces of the first pipe member 21 and the second pipe member 22 may be of any shape. The unevenness (screw knots) on the outer and inner surfaces of the third pipe members 23A and 23B may be of any shape. The unevenness (screw knots) on the outer surfaces of the first pipe member 21 and the second pipe member 22 may not be present. The unevenness (screw knots) on the outer and inner surfaces of the third pipe members 23A and 23B may not be present.

When the first pipe member 21, the second pipe member 22, and the third pipe member 23A, 23B do not have any irregularities (thread knots), as shown in FIG. 3, the first pipe member 21 and the third pipe member 23C, 23D are integrated by the frictional force between them, and the second pipe member 22 and the third pipe member 23C, 23D are integrated by the frictional force between them. The third pipe member 23C, 23D is a friction joint type joint that integrates the second pipe member 22 and the third pipe member 23C, 23D. In this case, the outer and inner shapes of the first pipe member 21, the second pipe member 22, and the third pipe member 23C, 23D can be any shape.

When measuring strain inside a concrete structure using optical fiber, there are two possible methods: (1) bundling and wiring optical fiber to rebar inside the concrete structure, and (2) adhering the optical fiber core to the surface of the rebar inside the concrete structure with adhesive. Method (1), bundling and wiring optical fiber to rebar inside the concrete structure, is the most commonly used method when measuring strain inside a concrete structure because it is easy to install.

This method uses a resin-coated optical fiber, but there have been reported cases where the optical fiber was pinched between rebars when the surrounding rebars moved after installation and broke, where the optical fiber was hit by a vibrator while concrete was being poured and broke, and where a worker tripped over a rebar or object while walking over the rebar and broke the optical fiber. Repairing a broken optical fiber requires a lot of effort, and there have also been cases where repairs could not be made due to construction conditions, so it is essential to develop an optical fiber wiring method that minimizes the risk of breakage.

Meanwhile, in method (2), in which optical fiber cores are fixed to the surface of rebar inside the concrete structure with adhesive, the risk of breakage that is a concern in method (1) is reduced by adhering the optical fiber to the rebar. Furthermore, if a crack occurs inside the concrete structure, the strain is measured through the rebar, which has the advantage of being able to measure the deformation behavior of a larger concrete structure compared to method (1).

However, when assembling multiple reinforcing bars with optical fibers attached in advance, it is necessary to connect the optical fibers using fusion or a connector after assembling the reinforcing bars. For example, when joining reinforcing bars with optical fibers attached, it is necessary to also connect the optical fibers at the joints of the reinforcing bars, which means providing a fusion part at the joint that is weaker than the optical fiber itself, but there is an issue in that no method has been established to protect the fusion part.

On the other hand, in this embodiment, the optical fiber connection structure 1 includes a first optical fiber 11, a first tube member 21 that houses the first optical fiber 11, a second optical fiber 12, a second tube member 22 that houses the second optical fiber 12, a connection portion 30 between the first optical fiber 11 and the second optical fiber 12, and third tube members 23A and 23B, and the first tube member 21 and the third tube members 23A and 23B are integrated, and the second tube member 22 and the third tube member 23A and 23B are integrated. 3A, 23B, and the connection part 30 is housed in either the first tube member 21, the second tube member 22, or the third tube member 23A, 23B, and is movable relative to the first tube member 21, the second tube member 22, and the third tube member 23A, 23B. Therefore, even if a force is applied from the outside to the first tube member 21, the second tube member 22, or the third tube member 23A, 23B, distortion is unlikely to occur in the connection part 30, and the possibility of optical fiber breakage can be reduced. In addition, in this embodiment, the possibility of optical fiber breakage can be reduced by a simple method of housing the first optical fiber 11, the second optical fiber 12, and the connection part 30 in the first tube member 21, the second tube member 22, and the third tube member 23A, 23B, and the workability of wiring optical fibers is improved.

In addition, in this embodiment, the first optical fiber 11 is fixed to the first tube member 21 so as not to be able to move freely, and the second optical fiber 12 is fixed to the second tube member 22 so as not to be able to move freely. Therefore, by integrating the first tube member 21 and the second tube member 22 with the structure, it is possible to measure the distortion occurring in the structure.

In addition, in this embodiment, the third tube member 23B is bent, and the first tube member 21 and the second tube member 22 integrated with the third tube member 23B extend in different directions from each other. Therefore, for example, when installing an optical fiber at the intersection of two reinforcing bars, the first tube member 21 is attached to one reinforcing bar, the second tube member 22 is attached to the other reinforcing bar, and the third tube member 23B is placed at the intersection, thereby reducing the possibility of the optical fiber breaking and improving the ease of installing the optical fiber.

The above describes an embodiment of the present invention, but the present invention is not limited to the above embodiment and can be implemented in various forms.

1...Connection structure, 11...First optical fiber, 12...Second optical fiber, 21...First tube member, 22...Second tube member, 23A, 23B, 23C, 23D...Third tube member, 30...Connection part.

Claims (4)

a first optical fiber for measuring strain ;
a first tube member that houses the first optical fiber;
a second optical fiber for measuring the strain ;
a second tube member that houses the second optical fiber;
a connection portion between the first optical fiber and the second optical fiber;
A third tubular member;
Equipped with
the first pipe member and the third pipe member are integrated, and the second pipe member and the third pipe member are integrated,
the connecting portion is accommodated in any one of the first pipe member, the second pipe member, and the third pipe member, and is movable relative to the first pipe member, the second pipe member, and the third pipe member,
an optical fiber connection structure, in which the first optical fiber is fixed to the first tube member so as to be unable to move relative to the first tube member by being integrated with the inner surface of the first tube member by an adhesive, and the second optical fiber is fixed to the second tube member so as to be unable to move relative to the second tube member by being integrated with the inner surface of the second tube member by an adhesive . 2. The optical fiber connection structure according to claim 1 , wherein the third tube member is bent, and the first tube member and the second tube member integrated with the third tube member extend in different directions from each other. an optical fiber connecting step of connecting a first optical fiber for measuring a strain accommodated in a first tube member and a second optical fiber for measuring a strain accommodated in a second tube member at a connecting portion;
a connection portion accommodating step of integrating the first pipe member with the third pipe member and integrating the second pipe member with the third pipe member so that the connection portion connected in the connecting step is accommodated in any one of the first pipe member, the second pipe member, and the third pipe member and can move freely with respect to the first pipe member, the second pipe member, and the third pipe member;
Equipped with
an optical fiber connecting method, in which, in the optical fiber connecting process, the first optical fiber is fixed to the first tube member so as to be unable to move freely by being integrated with the inner surface of the first tube member by an adhesive, and the second optical fiber is fixed to the second tube member so as to be unable to move freely by being integrated with the inner surface of the second tube member by an adhesive . 4. The optical fiber connecting method according to claim 3 , wherein in the connection portion accommodating step, the third tube member is bent, and the first tube member and the second tube member integrated with the third tube member extend in different directions from each other.

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